A hybrid vehicle may include an engine and a motor along a length of a driveline shaft that provides torque to a transmission. The engine may be selectively coupled to the motor via a driveline disconnect clutch so that the engine and motor may be operated separately or together to provide a desired driver demand torque. The motor may provide relatively small amounts of torque to drive vehicle wheels, or it may be operated as a generator to recharge an electric energy storage device. The engine may be activated to supply larger amounts of torque to vehicle wheels or to recharge the electric energy storage device via the motor operating as a generator. If the engine torque is increased and motor is decreased simultaneously to provide a driver demand torque over a short period of time, the engine torque may not increase at a same rate as the motor torque decreases, thereby causing a driveline torque disturbance. For example, a vehicle system controller may command an engine torque and a motor torque at a same time. The engine torque demand may be transmitted from the vehicle system controller to an engine controller and the motor torque demand may be transmitted from the vehicle system controller to a motor torque controller. Because the engine controller may receive its instructions at a different time than the motor controller due to communication network delays, the engine torque increase may not be compensated by the motor torque decrease. In addition, even if engine torque commands and motor torque commands were processed identically, engine torque production and motor torque production may vary due to response times of engine torque actuators and engine torque production being different than those of a motor. Consequently, a phase difference between the engine torque and the motor torque may develop, which may result in driveline torque disturbances that are objectionable to the vehicle's driver.
The inventors herein have recognized the above-mentioned issues and have developed a powertrain operating method, comprising: during engine run-up from cranking speed to a desired speed before a driveline disconnect clutch coupled to an engine is fully closed, commanding an engine torque to first torque bounded by a lower limit and an upper limit, the lower limit and the upper limit based on an accelerator pedal position.
By controlling engine torque limits during engine run-up from cranking speed to a desired speed and shortly thereafter in response to accelerator pedal position, it may be possible to provide a smooth progression of driveline torque during conditions where a driver expects the same. Additionally, during conditions of high driver demand where a driver reasonably expects a rapid change in torque production, the torque limits may be increased to improve driveline torque response. For example, when a driver is requesting a small amount of torque and the engine is started, a commanded engine torque may be heavily filtered so that engine torque and motor torque change slowly over time so as to reduce the possibility of disturbing the driver. Conversely, when a driver is requesting a larger amount of torque, commanded engine torque may be filtered less so that driveline torque response may be improved. In this way, engine torque and motor torque may be adjusted during engine starting and shortly thereafter to reduce the possibility of driveline torque disturbances.
The present description may provide several advantages. For example, the approach may provide reduce the possibility of producing driveline torque disturbances that may be objectionable to a driver. Further, the approach may provide a smooth transition between delivering all driver demand torque via a motor to delivering driver demand torque via the motor and an engine. Additionally, the approach may provide different torque limits during different engine starting phases so that the torque limits are appropriate for the requested maneuver.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.